Other meanings of Landsat program
Earth observation
The Landsat program is a joint NASA–USGS Earth-observing satellite program providing continuous land-imaging data since 1972. Its archive supports research and practical monitoring of agriculture, forests, water, urban growth, geology, hazards, and climate change, making it one of the longest-running records of Earth's changing land surface.1
The program was established to create a consistent, repeated view of Earth's land surfaces from space. Landsat 1, launched in 1972 as the Earth Resources Technology Satellite, demonstrated that satellite imagery could support resource surveys beyond weather forecasting; it was renamed Landsat 1 in 1975.1 NASA develops and launches the spacecraft and instruments, while the U.S. Geological Survey operates the civilian archive, processes data, and distributes products.2
The defining value of Landsat is continuity rather than a single spectacular image. Repeated observations allow analysts to distinguish temporary events from long-term change, although clouds, seasonal differences, sensor changes, and gaps in acquisition require careful comparison. The record covers natural and human landscapes on a global scale and is used alongside field measurements, aerial photography, and other satellite systems.
Landsat satellites measure reflected and emitted energy in several portions of the electromagnetic spectrum, turning those measurements into calibrated digital observations. Landsat 8 and Landsat 9 carry the Operational Land Imager, or OLI, and the Thermal Infrared Sensor, or TIRS; their principal multispectral bands have approximately 30-meter resolution, while panchromatic data provide finer spatial detail.3
Different bands reveal different properties: near-infrared responses help characterize vegetation, shortwave infrared bands assist with moisture and burn analysis, and thermal observations provide information about surface temperature. Landsat 7 added the Enhanced Thematic Mapper Plus, while earlier missions supplied the foundational observations that make multi-decadal studies possible.1 The satellites follow near-polar, sun-synchronous orbits, enabling broadly comparable illumination conditions on successive passes.
Landsat data are publicly available and are distributed through USGS services, including the Collection 2 archive, which provides standardized processing, improved geometric accuracy, and analysis-ready products.4 Researchers use the archive to map deforestation, crop conditions, irrigation, glacier retreat, wildfire scars, reservoir changes, mine expansion, and urban development. Governments and conservation organizations also use it for land-cover inventories, drought assessment, coastal studies, and disaster response.
Interpretation still demands expertise. A pixel may contain several land-cover types, atmospheric effects can alter apparent reflectance, and thermal measurements do not directly equal air temperature. Landsat's moderate resolution is powerful for regional patterns but may miss narrow roads, small fields, or individual trees. Analysts commonly combine Landsat with higher-resolution imagery, radar, field surveys, and statistical models rather than treating any one scene as definitive.2
The program's lesser-known strength is the scientific value of its archive, not merely its newest satellite. Reprocessing older scenes with improved calibration and geographic correction allows historical images to be compared more consistently with modern observations.4 The archive also preserves observations from missions whose instruments had different capabilities, creating both opportunities and methodological complications for long time-series research.
Landsat 9, launched in 2021, was designed to extend the record and operates in coordination with Landsat 8, improving the frequency of observations when their orbital paths are combined.3 Another important detail is the distinction between observation and interpretation: Landsat records spectral and thermal measurements, while products such as burned-area maps, crop classifications, or forest-loss estimates are derived analyses. This separation lets later researchers apply new methods to the same openly preserved measurements.
Landsat observations are measurements; derived maps and indicators depend on processing methods, validation data, and the question being studied.
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